I'm gonna do it...I'm gonna be honest knowing full well that my, albeit, honest response might open me up to ridicule and shame...that said here goes.
I have been using the Harbor Freight Special. There; I said it.
Not the expensive one either, the $10.00 job. While it lacks the frills that other more expensive models may have, digital readouts, etc., it does the job I need it to do. I have had such success with one, I bought (3) more.
Amazing deals on this 12V Automatic Battery Maintainer at Harbor Freight. Quality tools & low prices.
www.harborfreight.com